Crystal Structure of 2-Methoxymethyl-1,3-dithiane 1,1,3,3-tetraoxide

Abstract

Sulfon-containing dienophiles are extremely useful synthons in organic synthesis, 1,2 and are found to undergo a Diels-Alder reaction with cyclopentadiene to give predominantly an endo adduct in high yield. These cycloadducts were transformed into the norbornadiene and norbornene in quantitative yield. 1 A range of sulfon-containing dienophiles has been reported that acts as an acetylene equivalent in cycloaddition reactions. 2 The title molecule may be a useful starting material for preparing a new sulfon-containing dienophile.The title compound was prepared according to a literature method. 3 (1RS,2RS)-2-Methoxymethyl-1,3-dithiane-1-oxide (0.61 g, 3.69 mmol) was dissolved in dry diethylether (15 ml) at 273 K. Purified m-CPBA (m-chloroperoxybenzoic acid; 4.0 g, 18.4 mmol) in ether (20 ml) was added via a dropping funnel over 20 min. The reaction mixture was stirred for 2 h at 273 K. After 2 h the temperature was reduced to room temperature, and stirring was continued for a further 3 days at 298 K after which the resulting white solid was collected by filtration and washed with more dry diethylether. It was crystallized from ethyl acetate:methanol (5:95) (yield 0.298 g, 41%, m.p. 446 -448 K).The X-ray analysis results are given in Tables

Nucleophilic Additions to Alkylidene Bis(sulfoxides)—Stereoelectronic Effects in Vinyl Sulfoxides

“…The activation barrier for the ring-flipping between conformers 2-A and 2-B was measured for the parent alkylidene bis(sulfoxide) 2 c [a] Orientation of acceptor 11 as depicted in Scheme 3 and Figure 3. www.chemeurj.org (R = H) [37] by determination of the coalescence in deuterated methanol at 500 MHz. [38,33] The coalescence temperature was found to be À67 8C, corresponding to a free energy of activation of 40 kJ mol À1 and an activation barrier of 52 kJ mol À1 at this temperature.…”

“…[49] The NBO 3.1 program [42,43] was used as interfaced to the Gaussian 03 program package. [50] General: The synthesis of compounds 2 a, [5] 2c, [37] 3 a, [6] 5-7, [5] 13, [14] 16, [14] and 19 [6] was published elsewhere. Tetrahydrofuran (THF) was distilled over a sodium benzophenone ketyl radical and CH 2 Cl 2 was distilled over CaH 2 .…”